Brown University Professor Dov Sax discovered, in his most recent research, that there are now more naturalized plant species in New Zealand than native ones. That is, in New Zealand today, there are more varieties of plants brought over by Europeans than plants that grew there originally.
More provocatively, Professor Sax and his colleague Steven D. Gaines of the University of California, Santa Barbara, argue in a paper published this August in The Proceedings of the National Academy of Science that the introduction of invasive species to New Zealand has not, in fact, caused the extinction of native plants already on the island (which is more than can be said for the Europeans' invasive track record). A September 8 New York Times article notes that only three native plant species in New Zealand have gone extinct due to the introduction of competitive plants from abroad.
Sax and Gaines' results are controversial because they challenge the conventional fear that introducing invasive species into an area wipes out entire populations of wildlife that already existed there. In fact, Sax and Gaines found that in most cases, a native species' demise is due to a new predatory species in the area and not a competing one. Predatory species that feed on plants might include animals like foxes, cats and birds, whereas a competing species would more likely be another type of plant vying for the same resources as the plants around it.
Sometimes the introduction of competing species even results in the creation of an entirely new breed of plant--one example being Cordgrass in the salt marshes of North America. The introduction of a completely new species is usually seen as a good thing because it increases species richness of the ecosystem in which it lives.
BUT HOW NATIVE ARE THE NATIVES?
The belief that competition with other species leads to the extinction of pre-existing ones is based on the concept of species-based extinction: the idea that there are only so many niches in any given ecosystem and that a new species can occupy a niche only if the old species leaves or dies out.
However, Sax and Gaines found that total diversity sometimes increases in places where foreign competitors have been introduced into the ecosystem. According to the New York Times' review of the study, "Some invasions are indeed devastating, [but] they often do not set off extinctions. They can even spur the evolution of new diversity."
Sound anything like a basic principle of economics to you? Just as more firms entering into an industry increases the level of competition, the introduction of new species into an ecosystem spurs the process of evolution itself--perhaps raising the standard of evolutionary fitness of all species in the area over time.
But really, how native are the native plants in any specific ecosystem--don't all plant species have to come from somewhere? "Exotic species" is a term used by ecologists to describe organisms that are not indigenous to a certain location but were instead brought there by human transport and agriculture. Non-native species include new cultivated crops, foreign livestock, foreign seeds and anything else that grows where it wouldn't have cropped up by itself. Examples of exotic species in the Americas include three kinds of rat--the Black, Norway and Polynesian--zebra mussels, dandelions and ornamentals such as water hyacinth, salt cedar and purple loosestrife.
Dr. Sax explained to the Independent that distinctions between native and non-native species are arbitrary in some ways but that most scientists approached this problem by asking themselves this question: "Was this species directly assisted by humans in getting here?" If the answer is something like No, in fact this species blew over from Australia, then the plant is likely to be considered a native one.
EVOLUTION NOW JIVES WITH THE POPE (REALLY)
The times are a'changin' in realms outside of science, as well. Take the church, for instance; it was almost 150 years ago that Charles Darwin published On the Origin of Species, but only last Monday was he honored with a posthumous apology from the Church of England. The Catholic Church, however, has issued no such apology even though it now concedes that the theory of evolution is compatible with the Bible.
Although the Catholic Church does not take the Biblical description of creation literally, some other Christians do--particularly conservative Protestants in the United States. The Catholic Church would prefer to teach theistic evolution, which gives credence to evolution as a scientific theory but suggests that God could very well have thought of this too and that he was the one who put it all in action.
But evolutionary discussions and debates about exotic plants and invasive species aren't limited to scientific and religious debate only. They could very well turn out to be economic and political issues, too, as politicians and policymakers are forced to examine the impact human beings make on the environment.
The importance of our environment has been anything but muted in the current election. How much do our potential leaders really know--or care--about the environment? According to a 2006 article in the Anchorage Daily News, Sarah Palin said in regard to creationism and evolution: "Teach both. You know, don't be afraid of information. Healthy debate is so important, and it's so valuable in our schools. I am a proponent of teaching both."
Just last week, Pope Benedict spoke out against Biblical literalism at a conference in Paris. It's beginning to sound like we've come a long way from having to debate with people like William Jennings Bryan, who once said: "If the Bible had said that Jonah swallowed the whale, I would believe it." Even traditionally static institutions like the Church are adjusting their official attitudes toward scientific advancements and new theories. It is so important that politicians, whose responsibility it is to remain dynamic and flexible, also keep pace with new information and experts' opinions on the environment, one that that is proving to be more delicate than we'd like.
When asked whether he believed today's politicians knew enough about environmental matters in order to make intelligent decisions, professor Sax told the Independent: "Scientists often don't do a good enough job of communicating. The onus is on scientists. They can't just do their work and hope that a policymaker is going to read the work they publish in some obscure academic journal." He also noted that Rhode Island was lucky to have a senator like Sheldon Whitehouse who is so attentive to environmental issues. Let's hope that our newly-elected national leaders are attentive as well.
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